Optimization of ejector structure for the PEMFC hydrogen recirculation system

Due to its small size, no moving parts, and no parasitic energy consumption, the ejector is becoming an ideal solution for hydrogen fuel cell in hydrogen recycling loop. However, the high coupling characteristics of the circulating fluid and the supply fluid of the ejector under variable working conditions of the stack make it difficult to optimize the ejector. In this paper, for the coupling change of secondary pressure and back pressure of ejector under variable operating conditions of the stack, CFD fluid dynamic calculations and experiments are used to obtain the changes in the performance of the ejector under different NXP and working conditions, and to explore the evolution of NXP's influence on the performance of ejector under variable working conditions. The results show that the increase of primary flow pressure helps to improve the performance of the ejector. When the pressure is 4 bar, the entertainment ratio reaches a peak of 2.43 when NXP = -15.6 mm. At the same time, based on the research results, a method of calculate the optimal geometry structure of the ejector under varying operating conditions is established. The results are helpful for the matching design and optimization of the ejector and the stack under wide operating conditions.